2,4,6-Trimethyl-N-[1-(1H-pyrrol-2-yl)ethylidene]aniline

There are two independent molecules in the asymmetric unit of the title compound, C15H18N2, each of which features a syn disposition of the N atoms. In each molecule, the pyrrole and benzene rings are essentially perpendicular, with dihedral angles of 78.90 (9) and 79.96 (9)°. In the crystal, the independent molecules are connected by a pair of pyrrole–imino N—H⋯N hydrogen bonds, forming a two-molecule aggregate.

There are two independent molecules in the asymmetric unit of the title compound, C 15 H 18 N 2 , each of which features a syn disposition of the N atoms. In each molecule, the pyrrole and benzene rings are essentially perpendicular, with dihedral angles of 78.90 (9) and 79.96 (9) . In the crystal, the independent molecules are connected by a pair of pyrroleimino N-HÁ Á ÁN hydrogen bonds, forming a two-molecule aggregate. 316 parameters H-atom parameters constrained Á max = 0.18 e Å À3 Á min = À0.14 e Å À3 Table 1 Hydrogen-bond geometry (Å , ). antioxidant properties and outstanding activities for olefin polymerization (Small et al., 1998;Su et al., 2009a,b). As a five-membered analogue of the pyridine ring (Matsuo et al., 2001;He et al., 2009), pyrrole has been frequently introduced into the skeleton of bis(imino)pyridine ligands to design new ligands and corresponding metal complexes (Britovsek et al., 2003;Dawson et al., 2000). Bis(imino)pyrrole is usually prepared from Schiff base condensation of 2,5diacetylpyrrole and an aromatic amine (Matsuo et al., 2001). As a contribution to this research field, we present herein the synthesis of mono(imino)pyrrole from 2-acetyl pyrrole and 2,4,6-trimethylaniline, as well as the crystal structure of the title compound 2,4,6-trimethyl-N-[1-(1H-pyrrol-2-yl)ethylidene]aniline.

Related literature
The asymmetric unit of the title compound ( Fig. 1) comprises of two crystallographically independent molecules A and B. These two molecules are connected by a pair of nearly equal N(pyrrole)-H···N(imino) hydrogen bonds, Table 1. In each molecule the pyrrole ring and benzene ring are essentially perpendicular, with dihedral angles of 78.90 (9)° and 79.96 (9)°, respectively. The pyrrole rings of the molecules A and B present a nearly parallel spatial arrangement with a dihedral angle of 34.70 (11)°, and the benzene rings of the two molecules show a dihedral angle of 29.35 (13)°. Although the two molecules in the asymmetric unit are similar some minor differences in corresponding bond angles are evident, most notably C-N(imino)-C of 118.86 (19) and 120.2 (2)°, for A and B, respectively.
The crystal packing is stabilized by N-H···N hydrogen bonds (Table 1, Fig. 2) occurring between the independent molecules comprising the asymmetric unit.

Experimental
The reagents 2-acetyl pyrrole (0.1968 g, 1.80 mmol) and 2,4,6-trimethylaniline (0.2638 g, 1.80 mmol) were placed in a 50 ml flask. After a few drops of acetic acid were added, the mixture was subjected to radiation in a 800 W microwave oven for 3 min and 2 min on a medium-heat setting. The reaction was monitored by TLC, and the crude product was

Refinement
All H atoms were placed at calculated positions and refined as riding, with C-H = 0.93-0.96 Å, N-H = 0.86 Å, and with U iso (H) = 1.2 U eq (C, N) or 1.5 U eq (C) for methyl H atoms. In the crystal structure, there is an 33 Å 3 void, but the low electron density (0.18 e Å -3 ) in the difference Fourier map suggests no solvent molecule occupying this void.   Molecular packing of the title compound with hydrogen bonding shown as dashed lines.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.